To provide a method for accurately and simply manufacturing an optical semiconductor element having a p-type side electrode only on the flat surface of the upper part of a ridge on the overall surface, without using an accurate stepper or the like and without requiring a precise mark alignment.

The method for manufacturing the optical semiconductor element comprises the steps of forming banks 119A, 119B at both sides of the ridge 117, forming an insulator layer 108 on the overall surface, then forming a photoresist layer 109 thereon in a shape near flatness, exposing the layer 109 under the condition in which the photoresist layer on the region except the flat surface of the upper part of the ridge is half-exposed, and thereby exposing only the insulator layer 108 on the flat surface of the upper part of the ridge [(a)]. The method further comprises the steps of then removing the layer 108 and a cap layer 106 on the flat surface of the upper part of the ridge [(b)], and then forming a metal layer 111 having a thinner layer thickness than the layer thickness of the layer 106 [(c)]. The method also comprises a step of thereafter forming a p-type side electrode over the entire surface only the flat surface of the upper part of the ridge by lifting off.